1. Field of the Invention
The present invention generally relates to the diagnosis, prognosis, and severity of disease using medical images of a patient's body organs or structures of interest. In particular, the present invention relates to a system and method of measuring extent and severity of disease before, during and after treatment.
2. Description of the Background Art
Disease is any deviation from normal structure or function. A specific disease comprises symptoms manifested as specific biochemical, anatomical or physiological changes. Generally, a patient is non-invasively imaged using various imaging techniques or modalities (e.g., positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, fluoroscopy, x-ray, etc.) in the course of clinical examination to diagnose and determine extent and severity of disease in the patient. A measurement of disease extent is often a pre-treatment prognostic factor for overall survival. Serial post-treatment measurements of response to treatment are often stronger prognostic factors for predicting survival.
Cross or multi-modality imaging techniques (e.g., PET/CT, SPECT/CT, etc) provide physicians with composite information, which is the combination of two or more distinct registered data sets in which the properties of each data set are retained. Composite information provides physicians with the tools to localize, diagnose and stage underlying disease better than single modality information by taking advantage of attributes of both modalities. Multi-modality imaging devices are used to monitor functional and anatomical (structural) disease response (i.e., complete, partial, progressive and recurrent) to treatments. Physicians can quickly modify less effective therapy, thereby improving a patient's outcome and reducing the cost of ineffective treatment.
While functional image visualization of in vivo physiological and biochemical processes is often sufficient, volume-of-interest measurements quantitatively reflect the status of a disease. In either form (i.e., qualitative or quantitative), functional analysis often depicts the response to therapy earlier than structural changes. Generally, functional changes often precede structural changes by many days and weeks. The similarity of structural images in serial multi-modality images can serve as a basis for precise registration of serial multi-modality examinations. Registering the serial anatomical data inherently provides similar functional image registration precision.
Favorable and unfavorable prognoses are based on predictable changes of structural or functional biomarkers reflecting response of the diseased tissue to treatment. Biomarkers are detectable and measurable indicators of normal and pathological anatomic characteristics, physiologic, biochemical, or molecular parameters associated with the presence and severity of specific diseases. Physical examination, laboratory assays, and medical imaging use biomarkers to monitor health and detect disease. Since both the pathological and healing processes involve subtle increase or decrease in anatomical morphology, which occur gradually in time, a reliable measure of predictable change may be undetected, thereby reducing diagnostic accuracy. In many practical situations, the analyses of image-based functional biomarkers indicate a strong relationship of measured biomarker change to predictable specific disease even when the measurement is weak. Numerous attempts at complex computational methods that relate physiological, anatomical and molecular biological measurements to observed disease and healing processes have used logical, numerical, statistical and neural functions and systems of equations (e.g., expert systems, parametric mapping, neural networks and pharmacokinetics models) to assist in the diagnosis and prognosis of disease.
In an attempt to more accurately stage and diagnose disease, specialized nuclear medicine devices provide physicians with information about the structure and function of disease. Gamma cameras, single photon emission tomographs and positron emission tomographs are well known nuclear medicine systems that depict both tissue structure and function that is otherwise not visible by other medical imaging devices (e.g., CT, MRI, US, fluoroscopy). The application of nuclear medicine in the field of cardiology, specifically stress, rest, and redistribution myocardial perfusion SPECT imaging, exemplifies the efficiency and advantage of dedicated display and quantification of serial structural and functional images to diagnose disease and guide treatment. U.S. Pat. No. 5,803,914 to Ryals et al. discloses a method and apparatus for displaying data in a medical imaging system.
Often during diagnosis and treatment planning and monitoring, images from different modalities are inspected separately. Images from the same modality obtained at different times throughout the course of therapy are also inspected separately. Depending on the clinical requirements, a full understanding and ease of interpretation of disease requires superpositioning of anatomical and functional images of the patient. It is common practice to process patient images with the aid of a computer such that they are stereotactically reoriented and compared with normal subject images similarly processed. Automatic image alignment and volume-of-interest delineation by computer software and image visualization techniques, which are interactive and intuitive ease the visual interpretation task, are well known in the art. U.S. Pat. No. 5,568,384 to Robb et al., U.S. Pat. No. 5,672,877 to Liebig et al., U.S. Pat. No. 6,065,475 to Qian et al., and U.S. Pat. No. 6,249,594 to Hibbard disclose such systems and methods. Additionally, computer assisted methods for analyzing numerical patient data for diagnosing, screening, prognosing, and determining the severity of disease have been described, for example, in U.S. Pat. No. 6,306,087 to Barnhill et al.
Recently, multi-modality or combined devices (e.g., SPECT/CT, PET/CT, etc.) have been developed to provide both tissue anatomy and function in a single examination, with a patient in a fixed position, thereby improving the correlation of anatomical and functional images, and subsequent spatial localization of abnormalities. Such devices are disclosed in U.S. Pat. No. 5,391,877 to Marks, and U.S. Pat. No. 6,490,476 to Townsend et al. The capabilities provided by three-dimensional and even four-dimensional medical imaging modalities allow direct visualization of structure and function in vivo. However, the ability to extract objective and quantitatively accurate information from these biomedical images has not kept pace with the ability to acquire, produce, and register the images. None of the prior art references disclose the comparison of quantitative functional and structural medical image data to diagnose, prognose or determine the severity of disease using serial examinations obtained before, during, and after treatment of a patient.
Therefore, there remains a need for a system and methodology for overcoming the shortcomings of the prior art, such as a system and method of measuring extent and severity of disease before, during and after treatment of a patient.